The number of people seeking refuge as a result of environmental disaster is set to increase dramatically over the coming years. Ironically, given current attitudes, we in Britain will resist accommodating them, and yet they will have become refugees as a direct result of the way we in the west live. Global warming - more than war or political upheaval - stands to displace millions. And climate change is being driven by our fossil fuel-intensive lifestyles.

Though they have no official status, environmental refugees are already with us. They are people who have been forced to flee their homes because of factors such as extreme weather, drought and desertification. There are already more of them than their "political" counterparts - 25 million, according to the last estimate, compared to around 22 million conventional refugees at their highest point in the late 1990s. By 2050, mostly due to the likely effects of global warming, there could be more than 150 million.

In 2001, 170 million people were affected by disasters, 97% of which were climate-related, such as floods, droughts and storms. In the previous decade more than 100 million suffered drought and famine in Africa, a figure likely to increase with global warming. Many times more were affected by floods in Asia.

According to one study, at least five small island states are at risk of ceasing to exist. There are several serious unanswered questions. What will happen to the exclusive economic zones of such countries, and what status will their populations have? Where whole nations become uninhabitable, should they have new lands carved out for them? Or should they become the first true world citizens? If there is no state left, how can the state protect its citizens?

Sea level rise in the range expected by the intergovernmental panel on climate change would devastate the Maldives. Without real international legal protection, their people could become resented minorities in Sri Lanka, itself threatened, or India, with its own problems. On the small South Pacific island of Tuvalu, people already have an ad hoc agreement with New Zealand to allow phased relocation. Up to 10 million could be displaced in the Philippines, millions more in Cambodia, Thailand, Egypt, China, across Latin America - the list goes on.

The effects of these population movements are likely to be highly destabilising globally unless they are carefully managed. But, in spite of the scale of the problem, no one in the international community, including the UN high commission for refugees (UNHCR), has taken control of the problem. UNHCR says that, institutionally, they are too poor and that environmental refugees should be dealt with at the national level. It's true that most parts of the UN system are underfunded. Ironically this, like global warming, is mostly the fault of wealthy industrialised countries for either not raising or meeting their contributions.

But without action, the countries least responsible for creating the problem stand to carry the largest share of costs associated with environmental refugees. Bangladesh, one of the world's poorest countries, expects to have around 20 million people displaced. Creating new legal obligations to accept environmental refugees would help ensure that industrialised countries accept the consequences of their choices. In certain circumstances, the suggestion that the solution must lie at the national level could be absurd - the national level may be under water.

In the academic community, there has been much quibbling over definitions. Some would exclude environmental refugees from the protection the Geneva convention affords because, they say, recognition would be "unhelpful", overloading the existing refugee apparatus. The alternative, though, is to rely on current humanitarian relief operations that are widely considered inadequate. The convention could, however, already be used in its current form. Refugees are defined as people forced to flee across an international border because of a well-founded fear of persecution, or fear for their lives and freedom due to, among other things, membership of a particular group.

In terms of well-founded fears, drowning, homelessness or starvation would seem to fit the bill. In terms of membership of a particular group, any community or indigenous group similarly prone would also fit. Numerous countries already cannot afford to meet the basic needs of their people. Without proper environmental refugee status, the displaced could be condemned to a national economic and geographical lottery, and to the patchwork availability of resources and application of immigration policies.

There is a wide acceptance that current national policies would not be remotely capable of handling the scale of the problem. The environment can clearly be "a tool to harm". But to fit the argument for refugee status, can the harm be called intentional? Yes, if a set of policies is pursued in full knowledge of their damaging consequences, such as flooding a valley where an ethnic minority might live in a dam-building project.

The causes and consequences of climate change - who is responsible and who gets hurt - are now well understood. Actively disregarding that knowledge would be intentional behaviour. Current US energy plans, for example, will increase greenhouse emissions 25% by 2010. This is a question of justice in adaptation to climate change. Environmental refugees need to be recognised, and the problem managed before it manages us.